Using Apache with Suexec on Linux

Executing CGI Scripts as Other Users

January 21, 2000

The Apache Web server, like most if not all of the others in common
use today, lets you execute arbitrarily complex operations
through the use of CGI scripts. These can involve database
lookups, system administration functions, real-time control
of machinery, online payments, or almost anything else
you can think of.

Ordinarily, all of these things occur in the context of the user
running the Apache server itself (typically nobody
on Linux systems). This is fine when you're using a system that
is owned and used by a single entity...but what if you're an
ISP with multiple companies being hosted on your system? Or an
educational institution with faculty who want to be able to
execute their own scripts? Either everything has to be accessible
to the Apache nobody user, or you have to run
multiple instances of Apache on multiple ports and IP addresses,
one of each per user,
with the concomitant confusion of configuration files.

On the other hand, if the server is to be allowed to change its identity,
it needs to be done in a controlled manner, so that the chance
of compromising your system's security is kept to a minimum. (Remember,
Apache is usually started as root and only changes
to nobody later!)

The suexec (pronounced 'SUE-ex-Ek')
tool helps make this possible. It's found in the
src/support/ directory under your Apache source tree.

Assumptions in This Article
For the rest of this article, I'm going to make
the following assumptions:

your Apache source tree starts at
./apache-1.3/

your Apache ServerRoot is
/usr/local/web/apache

your Apache DocumentRoot is
/usr/local/web/htdocs

the username under which Apache runs (the value of the
User directive in your httpd.conf file)
is nobody

All of the cd and other shell commands in this article
that refer to directories use these locations.